Soaking fit purnace



F. W. MANKER SOAKING PIT FURNACE Aug. 9, 1,932.

Original Filed July l5. 1925 533313 Himno/vr F. W. MANKL.

SOAKING PIT FURNACE 2 Sheets-Sheet 2 Aug. 9, 1932.

Original Filed July 15, 1925 Ill lI/l Aug. 9, 1932y uNrrED STATES FORBES-T W. KANKER, OF ,DEIOIT, MICHIGAN, ASBIGNOB TO SURFACE COMBUBTION i `GOBPOIBAITCN', 0F TOLEDO, OHIO,

PATENT OFFICE A CORPORATION OF NEW YORK soaxnrrr FUBN'ACE v Original vl'e. 1,711,273, dated Apri1`30, 1929, Serial No. 43,698, illed `Tuly 1&5,v 1925. Application for reillue mea January is, mso. smal no. 420,615.

l This invention relates to improvements in furnaces and more particularly to that type vof furnace known as soaking pits, such as are `used in the steel industry for heating ingots prior to rollin Soaking pitilrnacesas formerly built have pit Where the steel is to be heated, the maxi'- fore reaching every 14 to 18 months.

mum temperature not being reached until the gases are about to pass out of the furnace. This condition occurs because of the inability of the gases to become thoroughly mixed bethe discharge or outlet port. The wear on t e ports is, therefore, very rapid due to high temperature and is one of the vfactors contributing to the high cost of main# tenance of furnaces of this type.

Regenerative furnaces also require attendants to reverse the flow of gases periodically and require rebuilding of the checker work Another disadvantage inherent in regenerative furnaces is the inability to control the mixture of gas and air in an one pit since the`pits are usually opy,ara in groups` of four and operated with one reversing unit. This results in slowing up operations when certain pits are charged with cold steel and others with hot steel.

The present invention has among its objects to provide a soaking pit furnace in which individual control may be had for each pit; to provide a construction which will make unnecessary the reversak'f gases and the attendant complicated flue construction, reversing valves and so forth; to provide a pit which may be fired from both sides simultaneously; to provide for the preheating of the air which is to be mixed with the fuel gas; to provide a simple means for regulating the amount of air which mixes with the fuel gas: to provide means for recirculating some of the hot products of combustion whereby to reduce the amount of fuel necessary to main? Fig. 2 is a horizontal sectionthrough the furnace taken on line 2-2 of Fig. 1, the view also showing, in plan, an adjacent pit of 'a series;

Fig. 3 is a vertical transverse section of the furnace on line 3.3 of Fig. 1; and

Fig. 4 is a detail view of the fuel-gas nozzle construction showing how the same may be water cooled.

The improved furnace includes a plurality of pits arranged side by side, each pit being a self-contained unit, and similar to the other pits. The drawings have therefore been con. fined to the illustration of a one-pit furnace construction except in Fig. 2 wherein the second pit of aseries has been indicated.

In the drawings, the soaking pit is indicated at 10. The bottom of the pit has a suitably supported ioor 11 on which the ingots 12 rest. ,Betweenthe floor proper and the in- \g'ots is a cinder bed 13. *"The topof the it is closed by a slidable cover 14 to permit t e insertion and removal of the ingots.

In each of two opposite side walls of the pit is provided an expanding throat or combustion chamber 16 which extends from side to side of the pit and has its bottom above the Hoor of the pit. The fuel mixture of gas and air enters the combustion chamber through a plurality of burner tubes 18 at the restricted end of the combustion chamber, said tubes being made of highly refractory material preferably carborundum. Mounted in axi alinement with these tubes are thekgas nozzles generally indicated at 20. These nozzles are preferably adjustably mounted inA the exterior wall of furnace, which wall is in spaced relation to the wall in which the tubes 18 are mounted, wherebv there is formed a vertically extending passage 22 between the two walls.`

' culating around the tiles in channels or paths 29 provided around the latter and finally entering the passage 22 into which the gas nozzles 20 extend.

The hot gases How from the pit to the rev cuperators by way of horizontally extending 10i The outer end of these tiles will, of course, bef

passages 32 and a connecting vertically extending passage 34. The passages 32 open into the pit slightly above the coke bed 13 thereof and below the Hoor 33 of the expanding combustion chamber 16. In order that the heat of the burnt gases may be utilized to the maximum they are first diverted through the upper part of the recuperator by a baille 38 in front of the same and then through the lower part of the recuperator from whence they pass to the stack by way of a passage 39 below the baflie 38.

Extending across the vertically extendin passage 22 leading from the recuperator an 1n almemeut with the horizontally extending passages 32 are hollow tiles through which a'sultable tool may be inserted from the outside of the furnace to clean said passages 32.

kept closed by suitable plugs when not in use.

Dust and the like which accumulates inthe bottom of the vertical passage 34 may be removed through a grate or frangible partition 36 above the balile 38.

As previously indicated the gas nozzles 20 are adjustable in the outer furnace walltoward and from the burner-tubes 18. Gas

y under high pressure is supplied to the nozzles by pipes 44, in order that the gas may entrain heated air from the supply passage 22. By ad]usting the distance between the point of the nozzle and the burner tube the amount of a1r entrained by the jet of gas can be varied torsuit conditions. If further adjustment of air and gas is desired the size of the burner tube may alsobe varied by removing the tube and replacing it by one of the desired size.

The, discharge openingof the nozzlemay also be varied if desired. By controlling the amount of airv entrained by the gas, the char-y acter of the atmosphere in the heating chamber 'may be readily controlled, thatis to say, the .atmosphere can be madea reducing or oxidlzmg vatmosphere at will, it being well understood by those skilled in the art that an oxidizing atmosphere .is obtained when the combustible mixture contains an `excess of air for 'complete combustion; that a reducing atmosphere is obtained when the combustible mixture contains a deficiency of air for complete combustion, and that a neutral atmosphere is obtained when the fuel gas and air are present in quantitative proportions for complete combustion. Ordinarily a reducing atmosphere will be desired so as to prevent the formation of scale on the ingots.

It will, of course, be readily understood by those skilled in the art that suiciently complete mixing of the air and gas will take place 1n passing through the tubes to render the mixture explosive, that is to say, propagation of vinflammation will be substantially instantaneousthroughout all .parts of the mixture as soon as the velocity of the mixture is reduced by expansion to the rate of iame propagation through the mixture. Localizedjheat on vthose sides of the ingots facing the burners 18 is prevented because of the reduction of velocity of the burning gases in the expanding combustion chamber 16. The heat is therefore a soft mellow heat, the heating gases flowing gently around all sides of the ingots,-the heating gases coming from the opposite combustion chambers meeting each other at the centerof the pit and gradually dropping down between the ingots (of which four are shown in a pit) and then passing out of the pit through the bottom side passages 32 on their way to the recuperators and stack,which passages are preferably below the combustion chamber 16 for a purpose hereinafter appearing.

' After the. combustible'mixture leaves the f. burner tubes, its velocity is lso r-educedby,

expansion in the small end ofthe combustion chamber 16 that combustion immedlately takes place in said smallv endp. To vfurther reduce the velocity of the combustion gases and to prevent localization of heat on the facef of the ingot the combustion chamber is fur-` ther" expanded Vas will be readily understood.

One of the important features of the 1n- `vention is the methodjof and means for recirculating somev of the products of combustion whereby to reduce the amount of/fuel needed to maintain the vdesired'temperature in the soakingpit or heating chamber 1Q. Once'they refractory material of which the pit '.is madehas become thoroughly heated, the

temperature of the burned gases ypassing out.

of the. pit will be relatively Lhigh.` Instead. therefore, of allowing all of the very 'hot gases `constituting the products of combustion Y `topass to therecuperator, a certain proportionlis' returned to the pit or, rather to the combustion chamber, thereto be reheated by the fresh burning'gas'es entering ythe pit.

Due tothe fact that the recirculated gases ai'c L v already very hot, a comparatively small since the combustible mixture issues from the tubes with considerable velocity, a portion of the burned gases will be induced to flow into the combustion chamber from the passages 32. The amount of burned gases flowing into the combustion chamber through the ports 40 may be readily controlled by regulating the effective size of the ports by means of cover tiles 4 2 resting on the floor 33 of the combustion chamber. The other portion of burned gases is allowed to flow to the recuperator to heat the air which is used to support combustion of the gases coming from the supply nozzle. Another effect of recirculating some of the burned gases in the manner specified is to further reduce the velocity of the burning gases coming through the tburner tubes and thus further mellowing the flames in the pit.

' As previously indicated the gas nozzles 20 are preferably water cooled. Cooling may be 'effected in any approved way but that indicated in Fig. 4 is preferred. The gas-supply pipe or nozzle proper is surrounded by outer and inner shells 45. and 46 respectively. Cold water enters the inner shell by way of a pipe 47, flows toward the jet end of the gas pipe 44 and then back through the outer shell and discharges by way of pipe V48.

structionof soaking pit furnaces provides many decided improvements over soaking pit furnace of the prior art and more particularly over soaking pit furnaces of the regeneratlve type. By firing the soaking pits from two opposite sides at the same time, a more uniform heat is .obtained in the pit and 'consequently all of the ingots in the pit will be equally heated; by entering the combustible mixture at points considerably removed from the pit proper and effecting a reduction of the velocity of the same by allowing them to expand in a combustion chamber of gradually increasing u volume before the gases enter the pit roper, localization of the heat on the face. of) the ingots facing the combustion chambers is effectually prevented and bv recirculating a regulated amount of the products of combustion the quantity of fuel revquired is reduced to the minimum.

It will also-be seen that a verysimple and eicacious method has been devised for controlling the mixture of air and gas which enters the combustion chamber, it being merely necessary to move the gas nozzles 20 It will now be seen that the present con-k toward or from their respective burner tubes 18. The closer the ti of the nozzle is to its tube the less air will drawn into the tube for mixing with the gas', and conversely, the

farther the tip is from itstube the greater` A will be the amount of 'air drawn in by the v'jet of gas. Furthermore bheating the air infa recuperator through wiicli the products of,y I l combustion are continuously assing, not only is the temperature of the air higher but a constantly uniform temperature of the air is obtained. This feature marks a decided improvement in the art and is one' of the factors contributing to the highV efliciency of the furnace.

While the improved furnace has been described with considerable particularity of detail, it is to be understood no limitations are intended except as may be defined in the appended claims.

What is claimed is:

1. In a furnace havingv a heating chamber 1n the form'of a pit, an expanding combustion .chamber in each of two opposite side walls of the pit, means at the restricted part of each of said combustion chambers for supplying combustible ases thereto, and means below each of said through which products of combustion may pass out of the pit. l

2. In a furnace having a heating chamber in the form of a pit, an expanding lcombustion chamber in each of two opposite sides of the pit, means at the restricted part of each of said combustion chambers for supplying combustible gases thereto, means extending below each of said combustion chambers through which products of combustion may pass out of the pit,and means for directing some of the products of combustion passing from the last-named means into the combustion chamber. Y

3. In a furnace having a heating chamber in the form of a pit, an expanding combustion chamber' in each of two opposite sides of the pit, means at the restricted part of each of said combustion chambers for supplying combustible gases thereto, means extending below each of said combustion chambers through which products of combustion may pass out f of the pit, and means'for directing some of the products of combustion passing from the last-named means into the combustion chamber at the restricted portion thereof.

4. In a furnace having a heating chamber in the form of a pit, an expanding combustion chamber in eachof two opposite sides of the pit, means at the restricted part of each of said combustion chambers for supplying combustible gases thereto, means extending combustion chambers A below each of said combustion chambers l' through which products of combustion may pass-out of the pit, and means for directing some of the products of combustion passing from the last-named means into the combustion chamber, and means forregulating the flow of the kproducts ofcombustion into the combustion chamber.

5; In a furnace having a heating chamber inthe form of a pit, an expanding combustion chamber in each `of two opposite side walls of the pit,..a plurality of tubes in the restricted part of each ofsaid combustion chambers through. which combustible gases may be passed, means in front of said tubes for regulating the gas and air content of the combustible mixture passing therethrough, means below each of said combustion chambers through which products of combustion may flow from the pit, and portsV through which some ofthe products of combustion may pass into2the combustion chamber after they have left the pit. l

6. In a furnace having a heating chamber in the form of a pit, the combination of a tube through which combustible rgases are passed,

an expanding-combustion chamber in which lthe gases are expanded before entering the pit, a gas nozzle in axial alinement with said tube and adjustable toward and from the latter, and an air supplying conduit between said tube and the nozzle.

7. In a furnace having a heating chamber in the form of a pit, an expanding combustion chamber leading away from the pit, a burner tube in the restricted part of the combustion chamber and through which tube combustible gases may be passed, a conduit below the combustion chamber throu h which products of combustion mayvpass rom the pit, and a p ort connecting said conduit with the combustion chamber at the restricted part thereof whereby some of the products of combustion may be entered into the combustion chamber.

8. In combination, a chamber to be heated, an expanding combustion chamber leading thereto, a tube of highly refractory` material in the restricted part of the combustion chamber, means for supplying highly heated air in front of said tube, and a gas nozzle adjustably mounted in front of said tube, the amount of air flowing into the tube being controlled by 'adjustment of the gas nozzle toward and from the tube, the entrainingaction of the gas flowing through the nozzle being the effective medium for carrying the air through the tube.

9. In a furnace having a soaking pit the combination with said pit, of a recuperator at each of two opposite sides of the pit, a combustion chamber in each of the said two opposite sides, means at. the closed end of each of said combustion chambers through which combustible gases may be passed, a passage between the respective recuperators and tubes for conducting heated air from the recuperators to the tubes, a gas nozzle for with respect to said tubes whereby the amount of air flowing through said tubes may be controlled by the entraining action of a jet of gas passing through said nozzles, and means for leadmg products of combustion out of the pit for passage through the recuperators, said meanscomprising passages located below said combustion chambers. e

10. In a furnace having a heating chamber, a combustion chamber opening on the heating chamber, a port at the closed end of the combustion chamber through which combustible gases may be entered thereinto, means extending below said combustion chamber through which products of combustion may pass outv of the heating chamber, and a port between said last named means and the combustion'chamber through which products of combustion may be entered into the combustion chamber.

1l. A method of heating ingots contained in a vertical pit comprising slmultaneously introducing into the pit above the bottom thereof and `from diametrically opposite directions a plurality of streams of burning gases, withdrawing the products of combustion from a plurality of diametrically opposite points below the points of introduction of the burning gases and injecting some of the withdrawn products of combustion into the burning gases before they enter the pit.

12. A soaking pit for ingots having continuously operated direct gas-fired burners on oppositesides thereof and means for continuously exhausting the waste gases from opposite sides of the center of said soaking pit in anni-directional path.

13. In a soaking pit for heating ingots, said pit comprising a refractory structure having an open-top rectangular ingot chamber formed therein and means for closing the top of the pit, the combination with said pit, of combustion chambers opening into the pit from opposite sides thereof and having a width substantially coextensive with the Width of the pit, means positioned at the outer end of each combustion chamber for discharging combustible mixture under pressure thereinto, the discharge opening of said means being of less cross sectional area than the adjacent end of the combustion chamber having an open-top rectangular ingot chamber formed therein and means for closing the f top of the pit, the combination with said pit, of combustion chambers opening intovthe pit from opposite sides thereof and having a width substantially coextensive with the l formed therein and means for closin width of the pit, a restricted passage at the bustion chambers inwardly of the discharge outer end of each combustion chamber, means end'thereof. lfor supplying combustible mixture under pressure to! said assage for discharge into the combustion c amber, and ports in vthe In testimony whereof I have hereunto set my hand.

walls of the pit through which lwaste gases may leave the pit. -v

15. In a soaking pit for heating ingot's, said pit comprising a refractory structure having an open-top rectangular ingot chambler t e trip of the pit, the combination with sai pit, o combustion chambers opening into the pit from opposite sides thereof and having a width substantially coextensive with the width of the pit, a restricted passage at the outer end of each combustion chambei'gmeans .for supplying combustible mixture. under pressure to said passage for discharge into whereby the mixture on issuin the combustion chamber, and ports in: the walls of the pit through which waste-gases may leave the pit, each combustion chamber at its outer end being relatively restricted as compared with its discharge end, said ,passage being centrally positioned with respect to dthe top and bottom walls of saidouter en 16. In a soaking pit for heating ingots, said pit comprising a refractory structure having an open-top rectangular ingot chamber formed therein and means for closing the top of the pit, the combination with said pit,

of combustion chambers opening into .the pit l from opposite sides thereof and having a width substantially coextensive with the width of the pit, means positionedv at the outer end of each combustion chamber for discharging combustible mixture under ressure thereinto, the discharge openingo said means being of less cross sectional area .than the adjacent end of the combustion chamber from said means may expand and burn be ore entering the it proper, and ports in the walls of the pit t ough which waste gases may leave the pit, said ports being beneath the combustion chambers.

17. In a soaking pit for heating ingots, said pit comprising a refractory structure having an open-top rectangular in ot chamber formed therein and means for c osin the top of the pit, the combination with sai pit, of combustion chambers opening into the pitfrom opposite sides thereof and having a width substantially coextensive with the width of the pit, means positioned at the outer end of each combustion chamber for discharging combustible mixture under pressure thereinto, the discharge 4opening' of said means being of less cross sectional area than the adjacent end of the combustion chamber whereby the mixture on issuin from said means may expand and burn be ore entering the pit proper, and means for introducing waste heating gases from the pit into the com- FoRREs'r w. MANKER.

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